Application of sodium bicarbonate abrasive jet technology for PCB desmear process: Conditions and simulation

Abstract

The desmear of blind hole is a critical process in Printed Circuit Board (PCB) manufacturing. An environmental-friendly, non-destructive and efficient sodium bicarbonate abrasive jet desmearing method was proposed in this study. The desmearing process was to drive the abrasive particles into the blind hole by pressurized air, and realized the cleaning of drilling dirt through collision. By comparing the cleaning effect, the process parameters (jet pressure, jet time, jet angle and jet distance) of sodium bicarbonate abrasive jet desmearing method were optimized, and the optimal process parameters were determined as 0.3 MPa, 10 s, 90° and 1 cm. Under the optimal process conditions, by comparing with the permanganate swelling method that widely used in the industry, it was confirmed that the cleanliness of sodium bicarbonate abrasive jet desmearing method could reach the commercial cleaning level while ensuring no damage, and the improvement of surface roughness (Ra = 7.57220 μm) was also at the same level. Through the research on the abrasive recycling process, it was detected that the recovery rate of abrasive could reach 80.18% by a simple recrystallization operation, which could significantly reduce the cleaning cost. The trajectory of abrasive particle in the blind hole was simulated by the gas-solid coupling discrete phase model (DPM), and the vortex cutting erosion desmearing mechanism based on the analysis of velocity vector characteristics was proposed. Due to its advantages of high cleaning efficiency, low damage, less pollution and recyclability of abrasive, the sodium bicarbonate abrasive jet desmearing method was expected to be applied in PCB blind hole desmearing process in the future.